Particularly, but not exclusively, the mobile seat of the present invention is for use in a motorized vehicle, such as an ambulance, helicopter, or other such vehicles which are subjected to abrupt movements capable of causing its occupants and the seat they are seated on to be thrown or displaced in a dangerous manner. It is known to provide a displaceable seat along a track of a rescue vehicle, such as an ambulance whereby the attendant can displace himself along a stretcher to attend to his patient while the vehicle is in motion. The attendant may be strapped to the seat and the patient is usually strapped to a stretcher which is connected to the floor of the vehicle. Such a system is, for example, described in German Patent DE 2641005 dated 1978. German Patent 2750406 also describes the construction of a displaceable chair secured to a rail and a caster to guide the seat and wherein the rail is provided with a belt connected to a coil at the end of the track to lock the seat in position. Accordingly, the seat can be locked in position regardless of sudden movement of the vehicle. French Patent 2635735 published on Mar. 2, 1990 also discloses a similar seat arrangement for securement in vehicles and wherein the seat may be locked to a desired position along a guide rail by means of a lever which is hand-operated by the user. In all of these publications, it is not permissible for the user person seated on the vehicle seat to displace himself in a hands-free mode while disconnecting and reconnecting a brake to immobilize the seat, and at its leisure, regardless of the comportment of the vehicle during transportation.